How do i make round bottle look more cubic with really soft edges?
Start with an octagon
WS Subdivide  a copy of it
Make another copy, and S scale its orthogonal vertices in to make it squarer.
Make a copy of that, and subdivide it, too.
With the copy, instead of subdividing it, CtrlShiftBbevel all its vertices.


When making the variations, they won't be side by side as illustrated: shift them up in Z to keep them out of the way, and vertically lined up. You can ShiftD make copies of those to work with, any time you like.



You now have all the profiles you will need for your bottle, bar a bit of tweaking.

Now assemble the bottle vertically, working your way down by  E sometimes extruding from copies of your profiles, and sometimes using  Ctrl E > 'Bridge Edge Loops' between them.

You can use the shipped add-on Loop Tools > circle to make the profile circular at the neck. 

The profiles shown here are: the neck, just above the ridge, and the smooth label area.

The closer the vertices on the profile are to one another, the sharper the crease in the final surface, after subdivision. You can vary the bevel on the squarer profile to achieve that. This example has 2 levels of Catmull-Clark, in a  Subdivision modifier, and the profiles are shown with the subdivision.